Self sealing fluid couplings consist of a pair of annular fittings each having a passage defined therein communicating at one end with a conduit system, such as a hose line, and each having an interengageable coupling end which intermesh upon the fittings being coupled and latched together. Each fitting passage includes valve structure, usually spring biased, which closes upon the fittings being uncoupled, and which engage during fitting interconnection to mutually open each other as the fittings are being coupled. The valve structure is usually either of a poppet type, or constitutes a sliding sleeve. Pressurized fluid systems wherein hydraulic oil, or the like, is pressurized by means of a pump normally utilizes pressure relief means to prevent excessive pressures developing within the fluid distribution system. Usually, pressure relief valves consist of a valve member biased into a closed condition by spring means whose biasing forces is adjustable, and upon the fluid pressure exceeding the spring biasing force the valve opens permitting the pressurized medium to be released, such as returned to the reservoir. Conventionally, pressure relief valves constitute a separate component of a fluid distribution system, and in a fluid distribution system utilizing self sealing couplings and pressure relief valves separate components for such purposes are employed resulting in relatively high manufacturing costs.
It is an object of the invention to incorporate pressure relief valve means into a self sealing coupling fitting wherein upon the fitting being uncoupled it will function for pressure relief purposes.
It is a further object of the invention to provide a combination self sealing and pressure relief valve structure within a coupling fitting wherein a single displaceable valve element is employed for both self sealing and pressure relief purposes.
An additional object of the invention is to provide a combination self sealing and pressure relief coupling fitting wherein pressure relief is provided with a minimum of expense without addition to the dimensions of a fluid conduit system.
In the practice of the invention a self sealing coupling fitting includes a passage through which flow is controlled by an axially displaceable sleeve valve element biased toward a valve seat. Upon the coupling fitting being coupled to a mating fitting the sleeve is engaged by the other fitting and axially translated to an open position during coupling. Upon the fitting being uncoupled the sleeve valve is automatically closed by its spring.
The sleeve valve includes radially disposed surfaces exposed to the fitting internal fluid pressure, and the fluid pressure acting upon such surfaces tends to bias the sleeve valve element toward its open position counter to the force produced by the associated spring. Upon such fluid produced force exceeding the spring force the valve is axially displaced from its associated valve seat permitting fluid to escape from the uncoupled fitting. The "relief" pressure at which the valve element opens is determined by the dimension of the valve element's surface upon which the fluid pressure is acting, and the force produced by the valve element spring. These variable factors are predetermined for each fluid system assuring dependable operation at the desired relief pressure.
Preferably, a dust plug is placed within the fitting upon being uncoupled to prevent foreign matter from entering the coupling, and a port defined in the plug closed by a spring biased valve permits fluid to escape the fitting upon being relieved from the fluid system, and this spring biased valve effectively functions to prevent foreign matter from entering the coupling fitting.